As is well known, electric harnesses each comprising wires of predetermined lengths with electric connectors crimped to their ends are widely used to make electric connection between electric devices. Such electric harnesses have a variety of wire lengths to meet different applications. In this connection electric harness producing machines are designed to crimp electric connectors to one or both ends of wires, and are designed to measure different lengths of wire.
FIGS. 11 and 12 show how the wire measuring part of a conventional electric harness producing machine measures wire length. Specifically, a length of wire W is pulled out of a wire supply reel (not shown) through a wire guide roller mechanism 40, and the wire W is caught and pushed down by the roller 42 of a looper 41 against the tension of the stretched wire W as indicated by arrow. The wire length W is determined in terms of the position at which the descending looper 41 holds the wire W with its roller 42.
The wire guide roller mechanism 40 comprises a single roller to permit the guiding of a plurality of parallel wires, and is designed to rotate at a fixed position relative to the wire supply reel. In FIGS. 11 and 12 means for conveying electric connectors R is indicated at 43.
The conventional wire measuring system can measure wire lengths easily, but it has the following deficiencies: when the looper 41 is raised subsequent to termination of measurement as shown in FIG. 12, and when the wire W thus measured is released from tension, the part of wire W which was stretched by the descending looper 41 so it extends from the roller 42 of the looper 41 to the wire guide roller mechanism 40 in FIG. 11, is curled as indicated by K in FIG. 12. The curled part of the wire length is liable to interfere the rising of the looper 41, and when a plurality of wires are measured, these individual wires are liable to tangle. Accordingly, the efficiency with which wire measuring and crimping can be carried out is lowered. The cause of curling is: when the roller 42 of the looper 41 is lowered, the wire W is pulled over the curved surface of the wire guide roller 40, which rotates at a fixed position, thus forming an angle between the upstream and downstream wire lengths relative to the wire guide roller 40. This causes curling of the downstream wire length upon putting the wire in a stress-free condition upon, raising the looper 41.